Can anyone tell me exactly what I'm supposed to be repeating... or how many times I'm repeating it? I'm on the first row of the gusset part, and I don't want to continue until I know exactly what I'm doing.

For some reason or another I can't post a comment on her blog, but I did leave a comment on her mittens pattern on Ravelry.

You are making an increase for the thumb. What you are repeating is a/the three row pattern. The 1st round with the M1 increases the 2nd and 3rd are knit.
Written in its entirity the pattern is as follows.